1. Field of the Invention
This invention relates to the fluxing of molten metals such as aluminum and alkali materials, e.g., Na, K, Ca, to remove impurities. More particularly, this invention relates to the removal of impurities such as hydrogen gas from molten alkali metals and molten metals such as a molten aluminum base alloy using a sparging gas in a system without moving parts.
2. Description of the Related Art
The production of aluminum base alloys has become of increasing interest due to the combination of lightweight and high strength which such an alloy can be made to possess. However, the formation of some aluminum base alloys is significantly more difficult than that of other aluminum base alloys due to the rapid adsorption of hydrogen gas by some alloys: reaction of some alloys with refractory linings in the furnace; and composition gradients in the cast ingot due to the propensity of some alloying metals to oxidize during processing of the molten alloy after the addition of the alloying metal.
The need for uniformity of composition usually requires stirring which may promote oxidation as well as further hydrogen absorption. The molten mixture is, therefore, preferably degassed after the mixing step to lower the impurity content of the melt by bubbling a sparging gas through the molten metal.
If the removal of impurities from the molten metal mixture is to be effective, however, it is important that there be intimate mixing between the sparging gas and the molten metal. Bruno et al. U.S. Pat. No. 3,839,019 discloses a process for purifying aluminum with chlorine gas using a particular apparatus with agitators and baffles to promote contact between the gas and the metal to be purified. Szekely U.S. Pat. Nos. 3,743,263 and 3,870,511 describe apparatus capable of purifying aluminum using inert gas which is introduced below the surface of the molten metal through a central passageway formed within a rotor which subdivides the gas into discrete gas bubbles and induces a circulation pattern within the molten metal which causes intense stirring.
It would, however, be desirable to provide a system which will optimize the mixing of the sparging gas and the molten metal or alkali material to maximize the efficiency of the removal of impurities therefrom using a passive impurity removal system integrated with the metal transport system and which would require no moving parts.